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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        let a=[2,6,1,7,4]
        let sum=0
        let ave=0
        for(let b=0;b<a.length;b++){
            sum+=a[b]//20
            ave =sum/a.length//4
        }
        document.write(sum,ave)
        //数组求最值
        arr=[2,6,1,77,52,25,7]
        let max=arr[0]
        let min=arr[0]
        let cha
        for(i=1;i<arr.length;i++){
            max=max>arr[i]?max:max=arr[i]
            min=min<arr[i]?min:min=arr[i]
            cha=max-min
        }
        document.write(max,min,cha)
    </script>
</body>
</html>